Carbon ribbon cartridges intended for typewriters include a feed reel about which the ribbon runs. In fitting the the cartridge to the typewriter, the feed reel is mated with a drive shaft in the typewriter so that the reel will be rotatably connected to the drive shaft, whereby the ribbon will be stepwise advanced in the movement of the drive shaft and feed reel.
In using ribbon cartridges in typewriters, there may be problems in fitting the cartridge into the typewriter due to the symmetrical axis of the reel not always being centered or coinciding with the symmetrical axis of the drive shaft in the typewriter itself. This is because the cartridge casing is generally attached to the typewriter and the dimension of the casing does not exactly agree with the distance between the symmetrical axis of the drive shaft and the locking position of the cartridge in the typewriter, due to the tolerances on the dimensions. This can cause a certain amount of deviation between the symmetrical axes of the feed reel and the drive shaft, thus causing eccentricity. The result will be increased wear on the drive shaft and feed reel, jerky advancing movement and increased frictional torque.